As it is well known, the space needed to store a bicycle, whether hanging or leaning against the wall, is the same as the width of its handlebar, usually between 55 and 60 cm. The standard width of the handlebars leads to a space loss, which gets worse when you need to store more than one bicycle, even if the direction of storage is alternated.
Another contributing factor to enlarge the space needed to store more than one bicycle are the pedals, which create an undesirable distance between bikes positioned side by side.
A similar and awkward situation occurs when we need to transport one, two, or more bicycles on a rear-mounted automobile bike rack.
The above mentioned problems could be solved by using folding bicycles.